In the manufacture of electrical devices such as integrated circuits and the like it is conventional practice to protect the finished device by hermetically sealing the surface of the device and encapsulating the finished device in a protective coating. The same coating of material is preferably used to both hermetically seal and encapsulate the electrical devices.
The coatings used for hermetic sealing and for encapsulation must be highly adherent to the electrical device, be free of defects such as cracks, pinholes, and the like and must be durable under a wide range of conditions of humidity and temperature.
Various materials have been suggested for use in hermetic sealing and encapsulating electrical devices. Certain plastics such as the polyimides are widely used but plastics tend to have pinholes and are not as durable as is required for many applications. It has also been suggested to use chemically vapor deposited glasses on the devices but this is expensive and the results are often somewhat erratic.
It has also been suggested to use mixtures of glass frit and an organic binder to form an initial layer on the electrical device. The organic binder is then burnt out and the glass frit is fused into what should be a continuous coating. This method has, however, not proven to be successful in that residual organic materials from the organic binder often remain in the fired glass frit and cause defects such as voids, pinholes, and discontinuities in the coating which make the final coating unsuitable for hermetic sealing and for protecting the electrical device.
What would be highly desirable would be a reliable method for forming continuous glass coatings which would hermetically seal and protectively encapsulate electrical devices.